This disclosure relates generally to methods and apparatus for drilling wellbores. More specifically, this disclosure relates to drill bits for use in drilling wellbores. Still more specifically, this disclosure relates to drill bits for use with bent housing motors.
In drilling a wellbore, such as for the recovery of hydrocarbons or minerals from a subsurface formation, it is conventional practice to connect a drill bit onto the lower end of a drill string. The drill bit is then rotated to form the wellbore. During drilling, a drilling fluid is pumped through the drill string to the drill bit. The drilling fluid passes through nozzles or orifices in the drill bit, into the wellbore, and then upward back to the surface through the annular space between the drill string and the wellbore. The drilling fluid serves to carry wellbore cuttings to the surface as well as clean and cool the drill bit.
In certain drilling operations, a downhole motor is incorporated into the drill string above the drill bit. The downhole motor utilizes the drilling fluid being pumped through the drill string to rotate the drill bit. Downhole motors are often used to increase the rotation speed of the drill bit and expedite drilling. In some operations, the downhole motor may be combined with a bent sub or bent housing that serves to tilt the drill bit at an angle from the centerline of the drill string. This tilt can be useful in changing and/or controlling the trajectory of the wellbore.
As the drill string is rotated, this tilt angle causes the central axis of the drill bit to rotate about an axis that is tilted relative to the bottom of the wellbore and/or relative to the wellbore trajectory. The cutters on the drill bit may sometimes not rotate about a fixed axis in the wellbore and are therefore not always in full contact with the wellbore as they would be during conventional drilling. Thus, there is a continuing need in the art for methods and apparatus for providing drill bits specially designed to work with bent motor housings or bent subs.